Technology advances in the electrical power distribution and electronics field have reduced the size of welding and plasma arc power sources. The large and cumbersome transformer power sources that are wheeled around job sites are being replaced by the more efficient inverter technology. The inverter technology provides a compact and lightweight welding or plasma arc power source ("power source") that provides power for multiple types of welding including, but not limited to, Stick, MIG and TIG and plasma arc cutting respectively. The inverters may be used as a welding or plasma arc power source in any industrial or commercial application.
The compact size and light weight of the power sources allow the power sources to be stacked in racks. The racks provide many advantages including: (1) maneuverability of multiple power sources at one time, (2) a comprehensive power distribution hookup to multiple power sources, and (3) a means to provide multiple power sources on a job site in a neat and safe manner.
Racks for inverter welding power sources are known in the prior art. The XMT.TM. Rack distributed by Miller Electric Mfg. Co., of Appleton, Wis. provides a rack made from steel that houses eight inverter power sources. The rack weighs about 1,700 pounds fully loaded with eight inverters and must be maneuvered using a fork truck, or a crane or be dragged, skidded are pushed around the job site. The XMT.TM. Rack provides a common power distribution bus with separate branch circuits protected by circuit breakers that power and isolate the individual inverters.
PewCon Inc., of San Diego, Calif. distributes a variety of modular racks that hold two, four, six or eight inverter power sources. The racks are made from tubular steel, and the larger racks weigh from about 600 to 750 pounds, loaded with power sources. The racks must be maneuvered using a fork truck, or a crane or be dragged, skidded or pushed around the job site. Each six and eight-unit rack provides a common power distribution box that provides power to the individual power sources.
The demand for power sources on a job site varies depending on the stage of construction, demolition or fabrication. Pre-construction or pre-demolition activity may not require a full complement of anticipated power sources. When construction or demolition begins in earnest, the need for power sources increases until the need is maximized during the height of construction or demolition. As the activity decreases, the need for the power sources also decreases. Furthermore, the demand for power sources at any particular location on a construction or demolition site varies as the work is completed in one area and commenced afterwards in another area.
Existing power source racks do not efficiently address the changing power source requirements during the entire schedule of a construction or demolition project. The XMT.TM. Rack is constructed to support eight power sources. The XMT.TM. Rack may be efficient during the peak activity of a job when eight power sources are required. But, during the beginning or end of a construction or demolition job, some of the power sources may not be needed (for example, four units may be idle) at the location of the rack or not needed on the job site at all. If four power sources are needed elsewhere, another eight-unit rack would be hooked up to a power supply and the four idle units might be disconnected and removed from the one rack and then mounted and connected to the new rack. Additionally, if the four idle units are not needed on the job site, but are needed at an alternate job site, the power sources would be disconnected, and transported and then connected to another rack elsewhere.
Furthermore, the XMT.TM. Rack weighs 1,700 pounds fully loaded with eight inverter power sources. The weight is a disadvantage on job sites when the rack must be relocated from one work area to another. Valuable time and resources, such as a crane or fork truck, as well as the required personnel, are wasted when the rack is relocated. If the rack must be relocated from one level to another on a building construction project, and a freight elevator either does not exist or is not rated for the weight of the fully loaded rack plus a fork truck it becomes necessary to use a crane to relocate the rack.
Even though PowCon provides different racks for various numbers of power sources, these racks still do not efficiently meet the changing requirements of power sources on a job site. If four power sources are needed at the beginning of the job, a four-source rack is sufficient. At the peak demand of power sources, an additional four-source rack can be installed, or an eight-source rack can replace the four-source rack. However, the additional four-source rack would require an external power supply hookup that is separate from the one that feeds the existing four-source rack. If the eight-source rack replaces the four-source rack, valuable time is lost transporting two racks, electrically disconnecting the power sources from the four-source rack and connecting those and four more units to the eight-source rack.